The last few days I have watched the dwarf miners in my city go from mining off the tree symbiosis to going idle. They was walk out of the inner city. It didn't matter if I logged out, and back in. Or if I went to world map, and then back into the city.

Before posting this, I wanted to see if there was a primary reason aside from just assuming it was a bug.

I noticed that only one out of the idle group would be at the edge of the map in some random location. One would always be in the city just next to a wall. Then I saw a treant in the south west of my city. 3 groups of Dwarf miners were circling it. When I told the Treant to move into the city they followed it.

I saw no point in having treants in the middle of my city since my settlement was right there, and it could be used as a drop off point. Ironic thing, When I placed just one treant in the city. All the dwarf miners functioned without a glitch

It may not sound like a problem, but why would the dwarfs be more inclined to go to a Treant outside my inner city than to my settlement? Why would half of them just stop working when I log back in until I placed a Treant in the city? Seems to me that there is a priority issue when mining.